In order to improve the efficiency of a gas turbine, the combustion temperature must be increased and in order to cope with increased combustion temperature, efforts have been made to develop various heat-resistant materials and cooling techniques for high-temperature members of the gas turbine.
As the combustion temperature increases, emissions of nitrogen oxide or so-called thermal NOx increase in an exponential manner, so it is necessary to take countermeasures against increase in thermal NOx emissions. As a technique to achieve low NOx emissions, a combustor with a multiple-injection burner (multi-cluster burner) structure which enables distributed lean combustion has been developed. The multi-cluster burner includes an air hole plate with many air holes and fuel nozzles arranged coaxially with the air holes. It decreases NOx emissions by mixing fuel and air as an oxidant quickly in a short distance of about several tens of millimeters in each air hole and thus generating a lean premixed combustion field.
An example of the related art in this technical field is the technique described in Japanese Patent Laid-Open No. 2013-108423 (Patent Literature 1). Patent Literature 1 discloses a gas turbine combustor including fuel nozzles and an air hole plate with air holes, in which a seal member is provided in an area where a liner and the air hole plate are fitted to each other; in an air hole of the air hole plate, an air hole portion located near a fuel nozzle has a straight pipe part coaxial with the fuel nozzle and shaped like a straight pipe and, and a portion of the air hole located near a chamber has an inclined part inclined at an inclination angle with respect to the axis of the chamber. The air hole plate is constituted of a plurality of members which include a straight pipe air hole plate member forming the straight pipe part and an inclined air hole plate forming the inclined part. The material of the straight pipe air hole plate member is different from the material of the inclined air hole plate member.